HOW CAN I USE SPEECH TO TEXT WITH MY TELEGRAM BOT???? HELPPP

Hi so I am working in a Telegram bot and I would like to use the Speech To Text Watson option, this is what I have already:

I just need to know what should I put on the function before de file buffer node :

I read in another post that I had to use the file buffer node to convert the audio file from Telegram into a buffer so the Speech To Text node recognise it. Wherever I send a voice message to Telegram I get this on the debut Tab:

really have no ideaaa. Could someone please help me? It is very important and it would be so Great!! Thanks to everyone!!!@@chughts